Cellular mechanisms of gastrointestinal motility are studied by biochemical and electrophysiological methods. Redox oscillations as pacemakers for slow electrical waves in longitudinal muscle of intestine will be examined. The nature of rhythmicity in circular muscle based on time and voltage dependent calcium conductance changes will be studied. The interaction between circular and longitudinal muscle layers and apparent amplification by circular muscle of slow waves generated in longitudinal muscle will be investigated by simultaneous recording from the two layers and by electron microscopic examination of coupling cells between layers. Calcium efflux will be measured in an effort to distinguish between Na-Ca exchange and active Ca pump in intestinal smooth muscle membranes.